Occipital plate for spinal fusion

ABSTRACT

Plate devices are provided for mounting to bone and receiving one or more spinal rods. The devices may include coupling members or rod receiving members coupled to the plate member and configured to have multiple degrees of adjustability in order to accommodate elongate connecting members of various orientations. The plate devices may also include quick locking features or locking devices that secure multiple points of articulation simultaneously.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/983,207, filed Dec. 31, 2010, which claims benefit of U.S.Provisional Application 61/298,488, filed Jan. 26, 2010, which is herebyincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates generally to devices for securing the ends ofspinal rods or other elongate fixation members to the skull of a patientfor spinal repair and/or fusion surgeries.

BACKGROUND OF THE INVENTION

Rigid or semi-rigid elongate members, such as spinal rods, may bemounted to the spinal column in order to stabilize or immobilizevertebrae of the spinal column for a variety of purposes. For instance,spinal rods are often secured to adjacent vertebral bodies via anchormembers in order to promote fusion of the two vertebrae as a treatmentfor degenerative disc disease, spondylolisthesis, spinal stenosis,fractures of the vertebrae, and other conditions. Limiting or preventingmotion of the vertebrae promotes the healing process. By removal of thedisc positioned between the vertebrae and limiting motion between thevertebrae, the adjacent boney surfaces are allowed to grow into oneanother and fuse together. Fusion devices may also be placed between thetwo immobilized vertebrae in order to facilitate the process of fusion.

When stabilizing portions of the spinal column, and in particular thecervical region of the spine, it is sometimes necessary to immobilizethe skull in addition to vertebrae. The same elongate rigid structuresused to link and stabilize the vertebrae may therefore be secured to theskull in order to keep the skull in an appropriate spatial relationshipwith respect to the spinal column. However, since the anatomy andthickness of the skull and its surrounding tissues are very differentthan those of the vertebrae and their surrounding tissues, the elongaterigid structures must be anchored to the skull in a different mannerthan that used for the vertebrae.

For instance, in many spinal stabilization procedures elongate rods madeof titanium or other materials are placed adjacent to the posterior sideof the spine and anchored in place using screws connected to some typeof coupling assembly. Examples of suitable coupling assemblies forposterior fixation systems are disclosed in U.S. Pat. No. 7,141,051;U.S. Published Application No. 2008/0045955; and U.S. PublishedApplication No. 2007/0225711. The screws used to anchor these devicesand other coupling assemblies are often relatively long, and are mountedto the pedicle area of the vertebrae with the shanks of the screwspenetrating deep into the vertebral body. The yoke portion of thecoupling assembly that is coupled to the screw and receives the spinalrod is nested between outwardly-extending boney processes so that theheight of the yoke is not noticeable.

When spinal rods are mounted to the skull, however, long screws andlarge coupling assemblies cannot be mounted directly to the skullwithout undue risk of penetrating the brain encased therein. Manycoupling assemblies also would prove extremely and unduly cumbersome ifmounted directly to the skull, and may even protrude significantly fromthe back of the head. In addition, the occipital region, which juts outat the base of the skull, is the only reasonable site at which to mountan internal fixation system, requiring that spinal rods connectedthereto be bent severely in order to be positioned along the occipitalregion and be connected to the occipital region in a manner similar tothe connection to the vertebrae.

Previous systems for coupling spinal rods and other elongatestabilization devices to the skull vary. However, most systems utilize aplate mounted to the occipital region of the skull that attaches to arod, cable, wire, plate, or screw mounted to a region of the spine. Inmost spinal rod systems, two spinal rods are positioned generallyparallel to the surface of the plate and then secured thereto by abracket or u-shaped receiving member. The plates are mounted to theskull with several small screws disposed along the full length and widthof the plate. Since the base of the skull angles inward toward thespine, the plates mounted to the skull are not parallel to the posteriorsurfaces of the vertebrae, and the spinal rods must be bentsignificantly away from the vertebrae in order to reach the occipitalregion in an orientation that may be mounted to the plate. For instance,the bending of spinal rods in order for them to properly be receivedrelative to an occipital plate is shown in the devices of FIGS. 1, 2,and 18 of U.S. Published Application No. 2004/0153070. In that device,spinal rods mounted along the vertebrae must be manipulated in order tofit precisely into receiver mechanisms aligned along the sides of aplate designed to be fixed to the occipital region of the skull. Thisbending of the rod can fatigue the rod material, and also makes itdifficult to reposition the elements of the stabilization system.

Even attempts to provide occipital plate devices with adjustability inorder to accommodate spinal rods of various orientations still generallyrequire significant manipulation and bending of spinal rods before theycan be secured to the plate structure. For instance, U.S. Pat. No.6,902,565 discloses a plate designed to be mounted to the occipitalregion of the skull by a plurality of short expansion head screws. Theplate receives a pair of rods that may be further mounted to one or morevertebrae. In many cases these rods are pre-bent so that the majority ofthe rods may be positioned parallel to the spine, with the ends benttransversely in order to be secured to the plate by a clamp plate orbracket. Some embodiments include plates that are bent in order toreceive the rods that are parallel to the spine. However, in all casesthe devices provided to clamp the rods in place on the plate aredesigned to accept the rod in only one position, so that any variationin angle or spacing of the rods caused by the patient's anatomy requiresbending of the spinal rods in order to properly secure them to theplate.

U.S. Published Application No. 2008/0051783 discloses a plate devicehaving a pair of u-shaped rod receiving members that protrude fromlateral wings of the plate. The wings may be shifted laterally andmedially, and the rod receiving members may rotate to adjust thedirection in which a connecting member (such as a spinal rod) isreceived. Therefore, the device does allow some adjustability in orderto receive the spinal rods. However, the spinal rods must be positionedso that they are generally parallel to the plate surface in order to fitinto the rod receiving members. Therefore, the ends of the rod must bebent away from the axis of the spine and into the u-shaped channels ofthe receiving members.

U.S. Pat. No. 6,524,315 discloses a plate secured to the bone by aplurality of screws. The plate is fitted with slotted bolts designed forreceiving a rod or cable. The base of the slotted bolt is recessed inthe plate at its base. A support platform may be fitted over the bolt tohelp hold the rod or cable. A nut fastens over the threaded end of theslotted bolt to trap the rod or cable within the bolt, securing it tothe plate. While the bolt may be rotated to adjust the direction of therod or cable, this adjustment affects only one plane, and does not allowfor adjustment of the angle of the rod or cable with respect to thesurface of the plate.

U.S. Published Application 2007/0233119 discloses a plate device withpolyaxial connector head assemblies including a connector body thatreceives a spinal rod and a connector head pivotably connected to theconnector body and configured to be secured to the plate so that theconnector assemblies provide limited polyaxial movement of the spinalrods with respect to the plate. However, the device does not allowmultiple types of movement to provide a highly articulated device.Furthermore, the coupling heads are relatively bulky and still hold thespinal rods relatively parallel to the plate surface.

Therefore, improved devices for securing spinal rods to the occipitalregion of the skull are desirable.

SUMMARY OF THE INVENTION

Fixation devices are provided herein for mounting to bone and receivingone or more spinal rods. Typically, these systems include a plate memberthat is curved to generally mate with the surface of the skull oranother boney region. The devices also include coupling members or rodreceiving members coupled to the plate member and configured to havemultiple degrees of adjustability in order to accommodate elongateconnecting members of various orientations. Although the devices may beconfigured to secure a number of elongate connecting members, such asrods, cables, wires, and the like, spinal rods will be primarilydiscussed herein. It will be understood, however, that this descriptionis not intended to be limiting, and that the invention is intended to beadapted for use with a variety of connecting members of differentshapes, sizes, and configurations.

In one aspect of the invention, a spinal rod mounting device may beprovided that includes a plate member having a plurality of openings forreceiving anchor devices and a pair of rod receiving members slidably orpivotably adjustable with respect to the plate member. In one preferredform, the rod receiving members are configured to receive a spinal rodsuch that the spinal rod can extend therefrom in a plurality ofdifferent directions relative to the plate member so that the rodreceiving members provide adjustability for the rods extendingtherefrom. Once the desired direction is selected, the rod can be lockedin place in the receiving member so as to fix the selected direction ofthe rod extending therefrom. The rod receiving devices also may bepositioned so that they can be secured to a portion of an elongatemember that is orthogonal to the surface of the plate member.

In another preferred aspect, the rod receiving members are slidablycoupled to the plate member. In another preferred form, the rod couplingdevices are mounted to the plate member in a manner that allows the rodreceiving devices to pivot with respect to the plate member. In a morepreferred aspect the rod receiving devices are both slidable andpivotable with respect to the plate member to provide multiple degreesof adjustability.

In another aspect, which may be optionally combined with other aspectsof the invention, the rods and/or rod receiving devices may beconfigured to be received by the rod receiving members in a plurality oforientations with respect to the rod receiving members. For instance,the rods may be provided with enlarged, curvate heads sized to bereceived in a pocket or cavity of the rod receiving device such that thecurvate head may be pivoted to a plurality of positions within theinterior of the cavity. Preferably, the cavity of the rod receivingdevices are provided with curvate interior surfaces contoured togenerally mate with the curvate exterior of the rod heads. Preferably,the rod heads and cavities are both partially spherical in order toprovide ball-and-socket connections between the spinal rods and rodreceiving members. This allows the axes of the elongate spinal rods tobe positioned to extend in a variety of different directions from therod receiving device without requiring bending of the spinal rods forthis purpose. The direction of the spinal rod may be locked with respectto the rod receiving device by a locking member, such as a set screw,non-threaded camming member, or other device that forces the spinal rodagainst the interior of the rod receiving member to create frictionalforces that inhibit movement between the rod and the rod receivingdevice. Combined with sliding and pivoting adjustability of the rodreceiving members, this ball-and-socket connection between the spinalrods and rod receiving device provides a highly adjustable system thatcan receive a pair of spinal rods having various orientations and holdthe pair of spinal rods in a fixed relationship with respect to a platemember attached to a patient's skull.

In another aspect, a plate device may be provided with a simple tooperate rapid locking mechanism to quickly secure the spinal rods inplace without separate adjustment of multiple parts. This allows theposition of one or more spinal rods to be fixed with respect to theplate device without adjusting multiple and/or complex parts.

The plate may be relatively thin and contoured to rest against the lowerrear surface of a patient's skull. The rod receiving members may eachhave an arm portion to serve as a connection point to the correspondingplate arms, and the rod receiving members may be secured to the arms ofthe plate by a bolt or other pivot member about which the rod receivingdevice is able to pivot. Each bolt is preferably disposed within a slotin an arm of the plate so that the rod receiving member is able to sliderelative to the plate member. In one aspect of the invention, the armsand corresponding slots of the plate member are disposed so as to extendaway from the center axis of the plate member so that the rod receivingdevices may slide along the slots of the plate arms in order to adjustthe distance between the rod receiving devices and the center of theplate member. Pivoting of the rod receiving devices allows the rodreceiving devices to be positioned at a plurality of positions along anarc centered around the bolt or other pivot member connecting the rodreceiving device to the plate arm. Combining the pivoting and slidingmovement of the arms and/or rod receiving devices allows for the rodreceiving devices to extend in a variety of different directions andspatial relationships with respect to the plate member and one another.Preferably, the bolt or other connector may be tightened to lock the armportion against sliding and pivoting, which in turn locks the positionof the rod receiving member. Alternatively, a separate locking mechanismmay be provided in order to prevent movement of the rod receivingmember.

The rod receiving device may include a pocket or cavity for receivingthe end of a spinal rod, or may have a channel that allows the spinalrod to pass therethrough. A locking member may be configured to fix theposition of the rod with respect to the rod receiving device. Forinstance, the locking member may be a set screw that is threaded intothe rod receiving device and clamps the spinal rod end therein, fixingthe position of the rod through friction by pressing the rod against theinterior of the rod receiving device.

In another aspect of the invention, a plate member may include a trackportion having guide tracks in which a pair of yoke members are slidablydisposed. The sliding of the yoke members along the guide tracks allowsthe distance between the yoke members to be adjusted so that the yokemembers may capture spinal rods adjusted to various distances from oneanother. In addition, the yokes may be rotatably and/or pivotablycoupled to the guide tracks in a polyaxial manner that allows forrotation and/or pivoting in one or more planes in order to easilycapture spinal rods so that they extend in a variety of differentdirections relative to the plate member, and specifically the trackportion thereof. For instance, the yoke may be provided with a swivelingneck portion that is slidably received in the track member and allowsthe yoke member to swivel in one or more directions with respect to thetrack member.

In one preferred form, the yoke member may rotate about an axis of theneck portion so that a rod receiving channel or opening in the yoke maybe positioned to face in various different directions with respect tothe direction in which the yoke slides along the track member. Inanother preferred aspect of the invention, the neck member forms aball-and-socket connection with the yoke member in order to allowpivoting of the yoke member in at least two planes in addition torotation about an axis of the neck portion. Locking members may beprovided in order to secure the spinal rods to the yoke members and tofix the position of the yoke members with respect to the track memberand plate member. In one aspect of the invention, a single lockingmember associated with each yoke member fixes the position of a spinalrod with respect to the yoke member and fixes the pivoted and rotatedposition of the yoke member with respect to the neck portion and/ortrack member. In another aspect, a single locking member secures theposition of two yoke members along the track member, such as byadjusting a clamp member that spans the length of the track member toexert frictional forces that prevent the yoke members from slidingrelative to the track member. Alternatively, separate clamping membersmay be provided to prevent the sliding of each of the yoke members.

In another aspect of the invention, the rod receiving members may becoupled to the plate member by telescoping members that allow thedistance of the rod receiving members from the plate member to beadjusted. This may include, for instance, a sleeve portion having anaxial bore coupled to the plate member and a post member coupled to therod receiving member, with the post member slidably received in theaxial bore of the sleeve portion. Alternatively, the sleeve portion maybe coupled to the rod receiving member and the post coupled to the platemember. The sleeve and post members also may be pivotably coupled to theplate member and/or rod receiving member in order to provide furtheradjustability to the positioning and orientation of the rod receivingmembers.

In another form, one or more rod receiving members may be coupled to aplate member by two or more ball-and-socket connections. A housing maybe provided to connect one ball-and-socket connection to the next. Inone preferred form, a single locking member is associated with eachhousing and is configured to lock the position of both ball-and-socketconnections with respect to the housing. The ball-and-socket connectionsalso may be pivotably and/or slidably connected to the plate memberand/or the rod receiving member to provide further adjustability to thedevice.

The anchors used to secure the plate to the patient's skull may beexpandable in order to increase their holding strength. For instance,the shank of the screw may be hollow and have one or more slits thereinrunning parallel to the axis of the shank so that insertion of a pin orother member into the hollow shank causes the exterior of the shank tosplay, expanding the width of the shank and applying additional lateralforce against the bone adjacent to the shank exterior. This lateralforce increases the load that may be placed on the screw in an axialdirection before the screw is stripped out of the bone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a first occipital plate device having sliding and pivoting rodreceiving members that receive a pair of spinal rods in a polyaxialarrangement.

FIG. 2 is a perspective view of the occipital plate device shown in FIG.1.

FIG. 3 is a perspective partially exploded view of the plate device ofFIGS. 1 and 2 from the front.

FIG. 4 is a perspective partially exploded view of the plate device ofFIG. 1 from the rear.

FIG. 5 is a plan view of the plate device of FIGS. 1-4.

FIG. 6 is a perspective view of the assembled plate device of FIGS. 1-5from the rear to illustrate the curvature of the plate member.

FIG. 7 is a partial cross sectional view of a rod receiving devicecoupled to a plate member.

FIG. 8 is a partial cross sectional view of the slidable couplingelements of the device of FIG. 2.

FIG. 9 is a perspective view of another adjustable occipital platedevice wherein rods are received in set orientations with respect to rodreceiving devices.

FIG. 10 is a perspective view of the device of FIG. 9 from the rear.

FIG. 11 is a side view of the device of FIG. 9.

FIG. 12 is a perspective partially exploded view of the device of FIG. 9illustrating the slidable members that couple the rod receiving deviceto the plate member.

FIG. 13 is a perspective partially exploded view of the device of FIG. 9from the rear illustrating the slidable members that couple the rodreceiving device to the plate member.

FIG. 14 is a perspective view of another occipital plate deviceincluding two slidable and polyaxial yoke members mounted to a trackmember that is coupled to a plate member.

FIG. 15 is a cross-sectional view of the device of FIG. 14.

FIG. 16 is an exploded view of the device of FIG. 14.

FIG. 17 is a perspective exploded view of the device of FIG. 14.

FIG. 18 is an exploded view of the yoke member and associated swivelbase illustrated in FIG. 14.

FIG. 19 is a cross-sectional view of the yoke member and associatedswivel base illustrated in FIG. 14 slidably mounted in a guide track ofthe device.

FIG. 20 is a perspective view of a plate device similar to that shown inFIG. 14.

FIG. 21 is an exploded view of the plate device of FIG. 20.

FIG. 22 is a perspective view of a multi-articulated plate device forsecuring spinal rods including telescoping rod receiving members.

FIG. 23 is a side perspective view of the device in FIG. 22.

FIG. 24 is a front view of the device of FIG. 22 with the locking capand spinal rod removed from one rod receiving device.

FIG. 25 is a perspective partially exploded view of the device of FIG.22.

FIG. 26 is a perspective partially exploded view from the rear of thedevice of FIG. 22.

FIG. 27 is a perspective view of a multi-articulated plate device havingarms with a plurality of ball-and-socket connections slidably mounted toa plate member.

FIG. 28 is a perspective view of the device from FIG. 27 from above.

FIG. 29 is a partially exploded view of the device of FIG. 27 showingthe components of the slidably mounted multi-articulating arms.

FIG. 30 is another perspective partially exploded view of the device ofFIG. 27 showing the components of the slidably mountedmulti-articulating arms.

FIG. 31 is a perspective partially exploded view from the rear of thedevice of FIG. 27 showing the components of the slidably mountedmulti-articulating arms.

FIGS. 32 and 33 are perspective views of the plate device from FIG. 27illustrating the sliding mechanism coupled thereto.

FIG. 34 is a perspective view of a plate device having sliding rodreceiving members and multi-function locking actuators.

FIG. 35 is a perspective partially exploded view of the device in FIG.35.

FIG. 36 is a perspective partially exploded view from the rear of thedevice in FIG. 35.

FIG. 37 is a front view of a plate device with rotatable arms.

FIG. 38 is a perspective exploded view of the device from FIG. 37.

FIG. 39 is a perspective exploded view of the device from FIG. 37 fromthe rear.

FIG. 40 is a front view of a quick-locking plate device having a singleactuator to lock a pair of spinal rods.

FIG. 41 is a perspective view of the device from FIG. 40.

FIG. 42 is a perspective exploded view of the device from FIG. 40.

FIG. 43 is a perspective exploded view from the rear of the device fromFIG. 40.

FIGS. 44 and 45 are perspective views of screws for mounting the platemembers disclosed herein.

FIG. 46 is a front view of another plate device having sliding rodreceiving members, flexible clamping members, and multi-function lockingactuators.

FIG. 47 is a front perspective view of the device shown in FIG. 46.

FIG. 48 is a rear perspective view of the device shown in FIG. 46.

FIG. 49 is an exploded view of the device shown in FIG. 49.

FIG. 50 is an illustration of a prior art occipital plate device forsecuring a pair of spinal rods.

DETAILED DESCRIPTION

The novel plate devices disclosed herein are better designed to receiveand hold spinal rod members than prior art plate devices configured formounting to the occipital region of the skull. For instance, toillustrate the contrast between the presently disclosed occipital platedevices and the prior art, a prior art device that requires spinal rodsto be bent substantially to be received by the plate device attached tothe skull is shown in FIG. 1. A clamping device 3 on each side of theplate 2 secures an end of a spinal rod 5 parallel to the plate surface.The clamping device may include a threaded set screw that clamps againstthe spinal rod, a bracket that is secured against the rod, or the like.A series of pedicle screws 7 secure the rods 5 to the vertebrae. Sincethe plate 2 and clamp devices 3 are mounted transverse to the axis ofthe spine, the spinal rods 5 must be bent outward away from the spine inorder to connect to the plate 2.

The plate devices provided herein have improved adjustability and/or aremore easily locked to fix the spinal rods in place.

One embodiment of an occipital plate member with adjustable rodreceiving heads is shown in FIGS. 1 through 8. The illustrated deviceincludes a relatively flat plate member 10 configured to be secured tothe patient's skull. Note that, although the plate member is relativelyflat, it need not be planar, and preferably has a slight curvature tomatch the surface of the occipital region of the skull. The plate mayalso be provided with grooves or notches 19 at particular points alongits surface in order to enhance the bendability of the plate at thosepoints in order to better match the curvature of the skull.

The plate member 10 includes a plurality of apertures 12 for receivinganchor members that secure the plate member 10 to the skull. Theapertures 12 may have tapered surfaces in order to center the anchormembers disposed therein. For instance, the rim 17 surrounding eachaperture may be curved or beveled in order to form a spherical orconical seating surface for the head of an anchor member. The plate bodyincludes a lower lobe portion 13 for mounting to the surface of theskull and lateral arm portions 4 that diverge from the surface of theskull when the plate 10 is mounted. The arms 14 serve as connectionpoints for rod receiving members.

In the device of FIGS. 1-8, rod receiving heads 20 are coupled to theplate member 10 by a sliding pivot connector 30. As shown in FIGS. 3 and4, the sliding pivot connector includes a bolt 31 and a sliding memberor washer 35 with an opening 36 in which the bolt 31 is received. Thebolt 31 has an enlarged head 32 and a narrower shank portion 33 that isslidably disposed in the slot or guide track 15 of the plate's lateralarm 14 and threadably connected to the opening 26 in the arm 25 of a rodreceiving device via a threaded shank portion 34.

The spinal rods 40 and rod receiving devices 20 shown in FIG. 2 aredesigned to interact in a polyaxial manner. The rods 40 each have apartially spherical or curvate head 41 that is enlarged with respect tothe body of the rod 40. The rod head 41 may be formed integral with therod 40, or may be a separate member that is secured to the rod 40 by athreaded connection, welding, or any other method. A cavity 22 (but seenin FIG. 3) in the rod receiving member 20 is configured to receive theenlarged head 41. The cavity may be semispherical or curved if desiredin order to receive the rod head 41 to form a ball and socketconnection, allowing the rod 40 to be pivoted to a number of differentangles with respect to the rod receiving device 20 while still havingthe rod head 41 fully seated within the cavity 22 of the rod receivingdevice. A locking member is provided in order to prevent the rod head 41form exiting the cavity 22. The locking member 27 may be a set screw orsimilar device, although the configuration of the locking member is notcrucial as long as it is capable of engaging the rod receiving member 20and securing the rod head 41 thereto. The locking member 27 shownincludes an internal tool interface 28 to facilitate rotation of thelocking member in order to advance the locking member along the threadedaperture of the receiving member.

In the illustrated embodiment, the locking member 40 is inserted into athreaded aperture 24 of the rod receiving device and into contact withthe rod head 41 positioned within the rod receiving device. When thelocking member 27 is fully threaded into the aperture 24, the leadingend of the locking member presses against the rod head 41, forcing therod head against the interior surface of the receiving device 20,applying frictional forces that prevent the rod 40 from furtherpivoting. This provides the device and the spinal rods connected theretowith structural rigidity in order to partially or fully immobilize theskull and spinal column. The cavity 22 of the receiving member 20 may besized to mate closely with the exterior of the curvate spinal rod head41 in order to increase the frictional forces that prevent pivoting ofthe rod 40.

The threaded aperture 24 for the locking member may, but need not,intersect with the opening 23 that receives the rod head 41, as long asthe rod receiving device 20 still has the structural integrity to holdthe rod head 41 in place once the locking member 27 is in a fully lockedposition.

The rod receiving device 20 may be positioned at various distances andangles with respect to the plate body 11 due to an articulated couplingbetween the receiving device 20 and the plate arm 14. Sliding of theconnector 35 along the guide track 15 in the arm of the plate (back andforth along directions A and B) adjusts the distance of the receivingmember 20 from the center of the plate. Since the guide tracks 15 of thetwo plate arms are disposed at oblique angles relative to the midline ofthe plate and one another, sliding of the bolt 31 therethrough may beused to simultaneously adjust the lateral distance between the two rodreceiving members 20 and the overall length of the plate device.However, the receiving devices 20 may also pivot about their respectivebolts 31. For instance, the rod receiving member 20 on the right side ofthe device in FIG. 2 may swing inward (medially) in direction C toreturn closer to the midline of the plate and the spine, and may swingoutward (laterally) in direction D in order to increase the spacing ofspinal rods received thereby. Through a combination of sliding andpivoting movement, the rod receiving members 20 may be adjusted to amultitude of positions to receive spinal rods of various spacings andorientations.

The sliding pivot connector 30 allows the receiving device 20 to belocked against both sliding and pivoting movement by manipulating asingle locking member. The turning of the bolt 31 of the sliding pivotconnector in a first direction clamps the rod receiving device arm 25against the plate lateral arm 14, locking the position of the twocomponents relative to one another. Rotation of the bolt 31 in anopposite direction releases the clamping force between the rod receivingdevice arm 25 and the plate lateral arm 14, allowing the rod receivingdevice 20 to pivot about the bolt 31. Therefore, a surgeon may swing thearm 25 of the rod receiving device 20 into position so that the cavity22 of the device properly receives a spinal rod, whereupon the surgeonmay tighten the bolt 31 in order to prevent further movement of the rodreceiving device 20 with respect to the plate member 20.

The sliding member 35, in addition to being disposed between the head 32of the bolt and the plate arm 14 and acting as a washer and to helpsecure the bolt 31, may also extend into the guide track 15 in order tobetter guide the sliding pivot connector. For instance, as shown in FIG.4, the sliding member 35 may include projections 37 on the undersidethereof that are fitted to be received in the guide track 15 of theplate arm 14.

FIGS. 3 and 4 illustrate that a lower lobe 13 of the plate body 11,which is positioned between the lateral arms 14 of the plate, curvesupward relative to the arms 14. The lower lobe 13 is configured tofollow the contours of the skull, maintaining contact with the bonewhile the arms 14 extend away from the skull at an angle. Thisconfiguration positions the rod receiving members 20 away from the skullto provide clearance for the receiving members to better receive thespinal rods connected to the spinal column.

The plate device of FIG. 1 is shown in plan view in FIG. 5. The slidingmember 35 and connecting bolt 31 may slide along guide track 15 in orderto extend the receiving devices outward in direction B. The rodreceiving devices 20 are also capable of pivoting about the bolts 31 inorder to swing laterally in direction D or medially in direction C. Eachrod receiving device 20 may be separately adjusted in order to bestreceive a spinal rod. The spinal rods are not disposed in the receivingmembers in this figure, providing an unobstructed view of the sphericalcavities 22 of the rod receiving members 20.

The occipital plate device of FIG. 1 can be seen in a perspective sideview in FIG. 6. This view illustrates the shape of the plate member,which allows it to lie against the surface of the occipital region ofthe skull. The lower lobe 13 of the plate curves upward in order to lieagainst the skull, while the lateral arms 14 are canted downward andaway from the skull to provide clearance for the receiving device arms25 that are positioned between the plate arms 14 and the skull. A groove18 is provided above the lower lobe 13 to facilitate bending of thelower lobe 13 for positioning against the surface of the skull.

A cross sectional view of the rod receiving device 20 is provided inFIG. 7. One side of one of the rod receiving members 20 is cut away toreveal the spherical cavity 22 and threaded aperture 24 therein. FIG. 8provides a cross section of a portion of the plate arm 14 and the arm 25of the rod receiving portion, illustrating how the two portions arecoupled together. As previously described, a bolt 31 is disposed in anelongate aperture that forms a guide track 15 in the plate body 11. Theenlarged head 32 of the bolt is nested on the sliding member 35 thatslides along the guide track 15. The shank 33 of the bolt passes throughthe guide track 15, and a threaded portion 34 of the bolt is threadedinto the arm 25 of the rod receiving portion. The head portion 32 of thebolt may be polygonal or otherwise shaped to facilitate turning with awrench, nut driver, or other instrument. The turning of the threading ofthe bolt 31 relative to the rod receiving device arm 25 forces the bolthead 32 and the arm 25 against the lateral plate arm 14, clamping theplate arm 14 between the sliding member 35 and the rod receiving devicearm 25. This clamping force creates friction that prevents the bolt 31and the rod receiving device arm 25 from further movement along theguide track 15, and also prevents pivoting of the rod receiving devicearm 25 about the bolt. The surfaces of the arms 25 and 14 may beroughened or otherwise contoured in order to enhance the locking forcebetween the two when clamped together.

An alternative embodiment of an occipital plate device is shown in FIGS.9-13. The embodiment illustrated in these figures is similar to theembodiment illustrated in FIGS. 2-8 except that the spinal rods arereceived in only one orientation rather than in a polyaxial manner. Theillustrated device includes a relatively flat plate member 110configured to be secured to the patient's skull, the plate memberincluding a main plate body 111, two lateral plate arms 114, and a lowerlobe 113 located between the lateral plate arms. Each of the main platebody and the lower lobe include a plurality of openings for bone screwsdesigned to mount the plate member to bone. The plate member illustratedhas a slight curvature to better match the surface of the occipitalregion of the skull than a flat plate.

In the device of FIGS. 9-13, rod receiving members 120 are coupled tothe plate member 110 by a sliding pivot connector 130. As shown in FIGS.3 and 4, the sliding pivot connector includes a bolt 131 and a slidingmember or washer 135. As with other sliding members disclosed herein,the sliding members may be made of any suitably strong material, but arepreferably made of a semi-flexible material such as nickel-titaniumalloys (Nitinol) and other similar alloys. The bolts 131 each have anenlarged head 132 and a narrower shank portion 133 that is slidablydisposed in the slot or guide track 115 of the plate's respectivelateral arms 114 and connected to one of the rod receiving members 120.

Each of the spinal rods may pass fully through a bore 122 in itsrespective rod receiving member 120. The bores 122 are positioned toreceive spinal rods in an orientation transverse to the surface of theplate body 111. A locking member 127 is received in an opening 124 ofthe receiving member and protrudes into the bore 122 from a transversedirection and applies force to each spinal rod in order to lock the rodin a fixed position within its respective rod receiving bore 122. Thelocking member 127 may be a threaded set screw or similar device,although the configuration of the locking member is not crucial as longas it is capable of engaging the rod receiving member 120 and securing aspinal rod therein.

The opening 124 for receiving the locking member should be formed tointerlock with the locking member 127. For instance, the embodimentshown in FIG. 12 includes a threaded locking member 127 and acorresponding threaded opening 124 in the receiving member. When thelocking member 127 is fully threaded into the receiving member 120, theleading end of the locking member presses against a rod that is disposedwithin the bore 122 of the receiving member, forcing the rod against theinterior surface of the receiving device 120, applying frictional forcesthat prevent the rod from sliding through the bore 122. This providesthe device and the spinal rods connected thereto with structuralrigidity in order to partially or fully immobilize the skull and spinalcolumn.

The locking members of FIGS. 9-13 have polygonal heads to facilitatemanipulation with a wrench or nut driver, although locking members withinternal drive recesses, as shown in FIG. 2, may alternatively be used.The locking members 127 may have a head portion of the same size andshape as that of the connecting bolt 131 of the slidable connector ifdesired, allowing manipulation of both types of members with the sametool.

The turning of the bolt 131 of the sliding pivot connector 130 in afirst direction clamps the bolt head and an arm 125 of the rod receivingmember against the plate lateral arm 114, locking the position of thetwo components relative to one another. The bolt 131 may be coupled tothe receiving member arm 125 in any manner, including a threadedinterface, welding, or a pivotable connection. Rotation of the bolt 131in an opposite direction releases the clamping force between the rodreceiving device arm 125 and the plate lateral arm 114, allowing the rodreceiving device 120 to pivot about the bolt 131.

As in the previous embodiment, the sliding member 135 is disposedbetween the head 132 of the bolt and the plate arm 114, thereby actingas a washer and helping to secure the bolt 131. In addition, the slidingmember also may extend into the arm guide track 115 in order to betterguide the sliding pivot connector 130. For instance, the sliding member135 may include projections 137 on the underside thereof that are fittedto be received in the guide track 115 of the plate arm 114.

As with the previous embodiment, the lower lobe 113 of the plate body111, which is positioned between the lateral arms 114 of the plate,curves relative to the arms 114. The lower lobe 113 is configured toapproximate the contour of the skull, maintaining contact with the bonewhile the arms 14 extend away from the skull at an angle. Thisconfiguration positions the rod receiving members 120 away from theskull to better receive the spinal rods connected to the spinal column.A groove 119 or the like may be provided to facilitate bending of thelower lobe or any other portion of the plate body 111.

In another aspect of the invention, a plate member 211 may be connectedto a track member 250 to which a pair of rod receiving members or yokemembers 270 are slidably connected, as shown in FIGS. 14-19. The slidingof the yoke members 270 along the track member 250 allows the distancebetween the yoke members to be adjusted so that the yoke members 270 maycapture spinal rods having various orientations and distances from oneanother.

The track member 250 includes a guide slot or guide track 252 along itsupper surface along which the yoke members 270 may slide. The yokemembers 270 may be coupled to the track member 250 in a manner thatallows for rotation and/or pivoting in one or more planes in addition tosliding in order to easily capture spinal rods positioned at variousorientations.

For instance, the yoke members 270 each may be provided with a swivelbase 280 mounted in the guide track 252, with the swivel basesconfigured to be coupled to the yoke members 270 in a manner that allowsthe yoke members 270 to be variously positioned. For instance, theswivel base 280 may allow the yoke member 270 to be rotated and/orpivoted in various planes in order to vary the orientation of the rodchannel 275 in the yoke member.

The yoke members 270 illustrated in FIG. 14 are U-shaped members withupright arms 276 that form a channel 275 therebetween sized and shapedto receive a spinal rod. The bottom of the channel 275 may be rounded inorder to cradle the spinal rod and provide line contact with the rod, ormay alternatively be of another shape or configuration. The yoke members270 also are configured to receive a locking member that secures aspinal rod within the channel 275. In the illustrated embodiment, theinterior surface of the yoke members 270 are provided with threads 277that interlock with complementary threads of set-screw type lockingmembers. Alternatively, the yoke members may be configured to receiveother type of locking members, such as an exterior nut. The yokes 270also alternatively may be configured to receive various types ofinterior or exterior non-threaded locking members, including but notlimited to bayonet-style locking members and the locking caps disclosedin U.S. Pat. No. 7,141,051; U.S. Published Application No. 2008/0045955;and U.S. Published Application No. 2007/0225711.

The yoke members 270 of the plate device 210 that secure the ends of thespinal rods may be of the same type provided for mounting to thevertebrae to secure other portions of the spinal rods, in order to allowfor interchangeability of parts. Alternatively, the yoke members may beof a different type with different locking members than are provided forsecuring the spinal rods to vertebrae.

The swivel base 280 that couples the track member 250 to the yoke member270 may have an enlarged portion disposed in a space 256 located belowthe guide track opening 255 of the track member, as best seen in thecross-sectional view of FIG. 15. This allows the swivel base 280 totranslate along the guide track 255 without disengaging therefrom. Inthe illustrated device, the swivel base 280 includes an enlarged baseportion 281 that is wider than the guide track opening 255. The baseportion 280 is provided with clearance to translate through an openspace 256 located below the guide track 255. The base portion isconnected to a narrower neck portion 285 sized and configured to beslidably disposed through the guide track 255. A head portion 282 isconnected to the neck portion 285 and serves as a coupling point for theyoke member 270.

The head of the swivel base advantageously may be partially spherical inorder to allow the yoke member 270 seated thereon to pivot in aplurality of directions. Due to the size of the base portion 281 of theswivel base 280, the head portion 282 must be provided with a suitablemeans for insertion into the yoke member 270. For instance, in theillustrated embodiment the head portion 282 of the swivel base 280 isinserted into the yoke member 270 from below. In order to allow the headportion 282 to be inserted but inhibit it from backing out of the yokemember 270, the head portion 282 is provided with a compression gap 283that allows the two halves of the head portion to deflect toward oneanother, reducing the width of the head and allowing it to pass throughan opening in the lower portion of the yoke member 270.

Once the head member 282 is positioned inside the interior space 271 ofthe yoke member, the halves of the head will resiliently shift outwardaway from one another, returning to their original position. Thisresilient shifting of the halves of the head portion 282 provides asnap-lock connection between the swivel base 280 and the yoke member270, coupling them together. At this point, a force must be applied tothe head portion in order to force the halves of the head together toallow the head portion to escape through the lower opening of the yokemember. In order to prevent the escape of the head portion, a pin orwedge may be forced into the gap 283 between the head halves, forcingthe halves of the head portion apart so that the overall profile of thehead portion is too large to exit the yoke member 270.

If desired, the head portion of the swivel base 280 may be configuredwith multiple compression/expansion gaps, or may be initially sized tofit easily into the yoke member from below and then expanded by theinsertion of a pin, wedge, or other expansion member that deforms thehead portion and increases its diameter to a point that it cannot exitthe yoke. Alternatively, other methods of positioning the head portion282 within the interior space 271 of the yoke member 270 may beemployed. For instance, the head portion may be provided as a separatecomponent that is loaded into the yoke member 270 from the top and thenconnected to the neck portion 285 or base portion 281, such as through athreaded connection.

The interior space of the yoke member 270 includes a seat portion 278that seats the lower portion of the swivel base head portion 282. Theseat portion 278 of the yoke member may be curvate or semispherical inorder to approximate the surface of the swivel base head portion 282,potentially providing multiple points of contact between the yoke memberand swivel base. Alternatively, the seat 278 of the yoke member may haveanother shape, and may only contact the swivel base head portion 282 atdistinct points if desired.

When the head portion 282 is spherical, as illustrated, the yoke member270 may be tilted in any direction and rotated about its axis to alignthe channel 275 of the yoke along various axes to receive spinal rods ofvarious orientations. Combined with the sliding movement of the swivelbase 280 along the guide track 255, the yoke member 270 is provided witha wide variety of possible positions. Preferably, the neck portion 285is sized and configured so as to provide the necessary strength tosecurely couple the track member 250 to the yoke member 270 while stillallowing the yoke member 270 to tilt to a relatively large range ofangles without interfering with the lower surface of the yoke member.

If desired, the head portion of the swivel base may be shaped to providetilting of the yoke member 270 in only a set number of directions. Forinstance, the head portion may be cylindrical to provide size-to-sidetilting of the yoke member 270.

The swivel bases 280 should be provided with a locking mechanism inorder to lock their lateral positions and firmly hold spinal rods inplace relative to the plate body 211. In the illustrated embodiment, thelocking mechanism includes a locking plate 275 and a locking actuator258. The illustrated locking actuator is a threaded bolt disposed in thetrack member 250 and threadably disposed in the locking plate 257 sothat rotation of the bolt 258 in a locking direction draws the lockingplate 257 upward toward the plate member 250. This upward movement ofthe locking plate 257 reduces the size of the space 256 below the trackmember 250, and clamps the base portions 281 of the swivel bases 280between the locking plate 257 and the track member 250.

The clamping force of the locking plate 257 should be sufficient toprevent further translation of the swivel bases 280 along the guidetrack 255. Advantageously, the configuration of the illustrated lockingplate allows for a single, centrally positioned locking actuator 258 tolock the positions of both swivel bases 280 simultaneously. Althoughshown as a bolt device, the locking actuator may be configured in avariety of ways, including but not limited to various rotatable onnon-rotatable non-threaded devices, for instance a bayonet stylemechanism with angled flanges or slots paired with complementarystructures in the locking member 257 and/or the track member 250.

The locking actuator may be provided with a mechanism that prevents itfrom separating from the locking plate. For instance, an anti-backoutpin 259 may be coupled to the actuator 258 and configured to abut thebottom of the locking plate 257 to prevent the actuator from exiting outof the top end of the locking plate. The anti-backout pin 259 may beconfigured to be snap-locked into a bore of the actuator 258, or may becoupled thereto by welding or other means.

The moving parts of the plate device of FIG. 14 can best be seen in theexploded view of FIGS. 16 and 17. FIG. 16 shows a front exploded view,where the locking member 257 and track member 250 are separated, withthe swivel bases 280 therebetween. Stop limits 297 are provided at eachend of the locking plate 257 in order to prevent the swivel bases 280from exiting the lateral ends of the guide tracks when the device isassembled. The yoke members 270 are shown in FIG. 16 separated from thehead portions 282 of the swivel bases 280. In addition, insert members290 are shown for each yoke member. The insert members are configured tosit atop the head portions 282 of the swivel bases 280 and assist inlocking the angular orientation of the yoke members 270.

Locking of the position of the yoke members may be accomplished inseveral different ways. The illustrated yoke members 270 are designed tolock to the generally spherical swivel base heads 282 at a setorientation by placing a downward force on the head portion (and arelative upward force on the yoke member 270) that presses the headportion 282 into the seat portion 278 of the interior of the yokemember, using friction to prevent further tilting or rotation of theyoke member 270 relative to the head portion 282. When a yoke member ispositioned at a desired angle and a spinal rod is received in thechannel 275 of the yoke, a locking member may be inserted on top of therod to close off the upper end of the channel. Preferably, this lockingmember applies a downward force upon the rod disposed in the channel,which then in turn transmits the force downward upon the swivel headportion 282 to lock it against the interior of the yoke member. Thelocking force may be transmitted from the spinal rod to the swivel basehead portion 282 directly or through a compression member, such as theillustrated insert member 290. The insert member provides more surfacecontact with the head portion 282 compared to the spinal rod alone.

The illustrated insert member 290 includes a concave upper surface 291for seating the rod and a spherical lower surface 292 for seating uponthe swivel base 280. The insert member 290 also may include rodreceiving arms 293 on its upper surface in which the spinal rod may besnap-locked prior to full locking of the yoke member 270. The exteriorof the insert member 290 may be equipped with wings 294 or otherstructures to guide the orientation of the insert 290 as it is disposedwithin the yoke member 270 so that the concave upper rod seating surface291 and the channel 275 of the yoke member are properly aligned. Inaddition, the wings 294 may snap-lock within the interior of the yokemember 270 so that the insert 290 exerts a compression force upon theswivel head portion 282 even prior to introduction of the spinal rod andlocking member into the yoke member 270. Configuring the insert member290 in this manner allows the yoke member 270 to be rotated and tiltedto a desired position and then provisionally locked in place prior toaligning the spinal rod with the yoke member.

A perspective exploded view of the occipital plate device 210 of FIG. 14is shown in FIG. 17. The guide tracks 255 are shown to have open ends253 that allow the swivel bases 280 to be slid into the guide tracksfrom the sides during assembly. Alternatively, the swivel bases 280 mayhave head portions sized to pass through the guide tracks 255 frombelow. When the locking plate 257 is assembled with the track member250, the swivel bases 280 are prevented from exiting the openings 253 bythe stop limits 297 of the locking plate 257. From this view, thecurvature of the arms 214 that connect the track member 250 to the platemember 211 may be seen. The arms 214 are curved so that when the platemember 211 is mounted to the occipital region of the skull, the arms 214hold the track member 250 away from the skull and toward the spine,positioning the yoke members 270 above the vertebrae to which spinalrods are secured. This positions the yoke members 270 so that they mayreceive spinal rods that are closely mounted parallel to the spinewithout requiring the rods to be bent outward away from the spine.

The yoke 270, swivel base 280, and insert member 290 are shown in detailin FIG. 18 in a magnified exploded perspective view. As previouslyindicated, the yoke member may include opposed upright arms 276 thatform a channel 275 therebetween for receiving a spinal rod or otherelongate member. A seating surface 271 may be provided at the bottom ofthe channel 275. A seating surface 278 at the bottom of the yoke memberinterior may be provided for seating the head portion 282 of the swivelbase 280. An opening 279 at the bottom of the yoke member 270 allows theswivel base 280 to be inserted into the yoke member 270, and the opening279 is preferably sized and configured to snap-lock with the swivel basehead portion 282.

The insert member 290 for the yoke member 270 is shown as generallycylindrical to generally match the interior of the yoke member 270.Although this is not necessary, in some instances it is advantageous forthe insert member to fit snugly in the interior of the yoke member 270,such as when it is desired for the insert member 290 to achieveprovisional locking of the swivel base 280 relative to the yoke withoutthe insertion of the spinal rod and a rod locking member. The insertmember upper surface may be concave as shown in order to seat the rodthereagainst with line contact, reducing stress risers on the rod, butother configurations are also possible. Flexible arms 293 may also beprovided to receive the spinal rod and hold it against the upper surface291 of the insert member. Slits 295 may be provided in the insert inorder to allow the insert member 290 to deform slightly as pressure isapplied and the member is compressed on the swivel base head portion282.

In order to couple the yoke member 270 to the swivel base, the headportion 282 of the swivel base is inserted through the lower opening 279of the yoke member. The slit 283 allows the head portion 282 to compressin order to fit through the opening 279. Once fully inserted into theyoke member interior, the head portion 282 either resiliently springsback to its original shape, or is splayed by inserting a wedge memberinto the slit 283. Preferably, even if the head 282 resiliently returnsto its original width after insertion into the yoke member a wedge, pin,or similar member is inserted into the head portion 282 in order toprevent the head portion from later collapsing and exiting the yokemember. In the illustrated embodiment, the head portion 282 includes acylindrical opening 287 for the insertion of a pin.

After the swivel base 280 is coupled to the yoke member 270, the yokemember may be swiveled to a desired orientation by rotation and/orpivoting of the yoke member 270 about the head portion 282 of the swivelbase 280. The ease with which the yoke member 270 swivels will be inpart determined by the tightness of the fit between the swivel base headportion 282 and the interior of the yoke member. If the two members fittightly together, some amount of friction will be required to rotate andpivot the yoke member 270, which may be advantageous in certainsituations since it reduces accidental movement of the yoke member.

The insert member 290 may be inserted into the top of the yoke member270 either before or after the insertion of the swivel base 280. Anopening or bore 296 passing through the insert may be provided in orderto allow manipulation of the swivel base 280 after the insert member 290is disposed in the yoke member. For instance, the bore 296 through theinsert member allows access to the cylindrical opening 287 of the swivelbase for inserting a wedge member therein. When the insert member isintroduced into the yoke member, the concave upper surface 291 of theinsert member should be properly aligned with the channel 275 of theyoke formed by the upright arms 276 in order to allow the assembly toproperly receive a spinal rod. Wings 294, grooves, or other structuresmay be provided in order to maintain proper alignment of the insertmember. As can be seen in FIG. 18, corresponding structures may also beprovided on the interior surface of the yoke, such as the grooves thattraverse the threading 277 on the interior of the yoke arms 276. The rodmay be seated on both the concave surface 291 of the insert member andthe concave seating surface 271 of the yoke member, or only on thesurface of the insert with a clearance between the rod and the yokeseating surface 271. Alternatively, the rod may be seated only on theseating surface 271 of the yoke, or the assembly may be designed withoutan insert member so that the rod presses directly against the head 282of the swivel base 280.

When a spinal rod is positioned in the channel 275 of the yoke member,downward force applied to the rod forces the insert member 290 disposedbelow the rod into contact with the swivel base 280. One or more slits295 may be provided in the insert member 290 so that the insert maydeform slightly as it is compressed onto the swivel head portion 282. Tosecure the spinal rod within the yoke channel 275, a locking member maybe provided that blocks the upper end of the channel and maintains adownward force upon the rod, which transmits the force to the insertmember 290, which compresses against the swivel head portion 282 andforces it against the seating surface 278 of the yoke member,frictionally locking the position of the swivel base 280 and the yoke270 relative to one another. The locking member should be designed toengage the yoke 270 so that it is capable of holding the spinal rod inthe channel 275. For instance, the illustrated yoke 270 has interiorthreads 277 configured to receive a set screw by rotational insertion.Recesses 272 may be provided in the exterior of the yoke member in orderto provide a gripping surface for holding the yoke in place while thelocking member is engaged.

As an alternative to a set screw locking device, the yoke 270 may beconfigured to receive other types of locking caps, such as thenon-threaded locking caps disclosed in U.S. Pat. No. 7,141,051; U.S.Published Application No. 2008/0045955; and U.S. Published ApplicationNo. 2007/0225711. The yoke member 270 and its corresponding lockingmember may be the same as or different than the coupling members used tosecure other portions of the spinal rods to the vertebrae of thepatient.

The assembled yoke member 270 and swivel base 280 are illustrated in thecross sectional view of FIG. 19. The base portion 281 of the swivel base280 is clamped between the locking plate 257 and the track member 250,with the neck portion 285 and head portion 282 protruding from the guidetrack 255 of the track member. The yoke member 270 is pivotably mountedto the head portion 282 of the swivel base, which is seated against theinterior seating surface 278 of the yoke member. The insert member 290is disposed in the interior of the yoke member and seated on top of theswivel base 280.

A similar occipital plate device 311 is illustrated in FIGS. 20 and 21,and includes a pair of yoke members 370 slidably and pivotably coupledto a guide track 355 of a track member 350 that is mounted to a platebody 311 having a plurality of openings 312 for anchor devices such asscrews. As can be seen, the arms 314 that connect the track member 350to the plate member 311 are of a different shape than provided in theprevious embodiment, and serve to hold the track member 350 closer tothe skull when the plate member 311 is mounted to the occipital regionof the patient's skull.

As with the previous embodiment, the device shown in FIGS. 20-21includes a single actuator 258 to selectively inhibit lateral and medialtranslation of the yoke members 370. The exploded view of FIG. 21 alsoshows pin members 389 that are insertable into the head portions 382 ofthe swivel bases 380 in order to prevent compression of the headportions and maintain positioning of the head portions 382 within theirrespective yokes 370. If desired, the head portions 282 and pins 389 maybe configured so that the pins splay the halves of the head portions 382when inserted to an extent that causes frictional engagement between theexterior of the head portions 382 and the interior surfaces of theirrespective yoke members 370.

Also illustrated in FIG. 21 is the anti-backout pin 359 that maintainsthe coupling between the locking actuator 358 and the locking plate 357.The actuator 358 is disposed in an opening 351 at the center of thetrack member and then threaded into a threaded aperture 398 of thelocking plate. Advancing the threads of the actuator 358 through thethreaded aperture 398 pulls the locking plate 357 upward in order toclamp the swivel bases 380 against the track member 350. Theanti-backout pin 359 includes two gripping members 359 a and 359 bconfigured for one-way linear insertion into an axial bore of theactuator 358. The leading surfaces of these gripping members are slopedin order to force the members to compress together when inserted intothe actuator 358 in a forward direction, but once inserted past awidened portion of the interior of the actuator the gripping members 359a and 359 b spring apart. The trailing ends of the gripping members areshaped to prevent backward translation of the anti-backout pin 359. Oncecoupled to the actuator, the enlarged base of the anti-backout pin 359prevents the locking plate 357 from separating from the actuator 358.

Another example of a highly adjustable occipital plate device 401 isshown in FIGS. 22 through 26. The device 401 includes a plate member 410with a plurality of holes for receiving anchor members, a pair oftelescoping arms 430 pivotably mounted to the plate member 410 by aswivel connection 420, and rod receiving heads 440 and 460 mounted tothe telescoping arms.

The telescoping arms 430 each include a housing portion 431, an innerarm 435, and a length adjusting member 437. The inner arm 435 isconfigured to translate and rotate with respect to the housing member430, allowing for the length and orientation of the arm 430 to beadjusted. When the desired length and orientation is achieved, thelength adjusting member 437 may be actuated in order to set the positionof the inner arm 435 relative to the housing 430. The length adjustingmember 437 may be a set screw or other device capable of clamping theinner arm 435 to the interior of the arm housing 431 in order to inhibitrelative movement of the components of the telescoping arm assembly 430.

In FIG. 22, two different types of rod receiving heads are shown. Thefixed rod receiving head 460 on the right hand side of the device doesnot pivot or rotate with respect to the telescoping arm and has achannel 465 to receive a spinal rod 470. The channel 465 may be closedoff by the attachment of a locking cap to the rod receiving head 460.The locking cap may take various forms.

The variable rod receiving head 440 on the left of the device is coupledto an elbow joint 436 of the inner arm 435 of the telescoping assembly430, and is able to rotate thereabout. A channel 445 is provided in thehead 440 to receive a spinal rod 470. The spinal rod 470 may be lockedinto place in the rod receiving head 445 by a locking cap 450, which maybe rotatably coupled to a wedge plate 455 that is positioned adjacent tothe spinal rod 470.

A perspective view of the device is shown in FIG. 23, illustrating thepositioning of the telescoping assemblies 430 relative to the platemember 410. FIG. 24 illustrates the telescopic adjustment of one of thetelescoping arm assemblies 430, positioning the fixed rod receiving head460 further away from the plate member 410. The locking cap 450 is showndisengaged from the variable rod receiving head 440, allowing the spinalrod 470 to be removed therefrom. Threading 449 is provided about theupper portion of the variable rod receiving head 440 in order to securethe locking cap 450 by rotational locking of threads on the interior ofthe locking cap 450 and the threading 449 on the rod receiving device. Awedge plate 455 may be provided for placement between the locking cap450 and the surface of the spinal rod 470. The illustrated wedge plate455 includes a concave recess 457 on the underside of the plate to matewith the surface of the rod 470, and also includes an optional couplingfeature 456 for rotatably coupling the plate 455 to the underside of thelocking member 450, such as by a post or pin received in the couplingfeature 456.

The telescoping assembly 430 is shown partially disassembled in FIGS. 25and 26 in order to better show its relationship to other portions of thedevice. FIG. 25 illustrates a perspective view of the device from thefront (the side that faces away from the skull when mounted), whereasFIG. 26 shows a perspective view of the device from the rear (the sidethat is placed adjacent the skull for mounting).

The annular array of teeth 480 provided around a portion of the innerarm 435 is designed to interact with complementary teeth 481 disposed onan interior surface of the adjustable rod receiving head 440 in order tofacilitate gripping of the inner arm by the receiving head. When aclamping force is applied to a spinal rod received in the receiving head440 by the locking member 450, the inner arm 435 is pushed downwardrelative to the receiving head 440 and the receiving head 440 is pulledupward relative to the inner arm 435, meshing teeth 480 together withteeth 481 to inhibit rotational movement of the receiving head 440 aboutthe inner arm 435. Until the locking cap 450 is secured to the receivinghead 440, however, the receiving head may be rotated forward andbackward to align the channel 445 for receiving the spinal rod asdesired relative to the plate member. In the middle of the toothedregion 480 of the inner arm 435 is an annular recess 485. The spinal rodcaptured by the rod receiving head will be seated against this annularrecess when fully seated. In addition, a pin 487 is provided that may beinserted into the rod receiving head 440 through a bore 449 in the sideof the receiving head. When inserted, the pin lies in the underside ofthe annular recess 485, on the opposite side of the annular recess thatthe spinal rod rests against, and prevents the rod receiving head 440from shifting from side to side along the inner arm 435. In this manner,the receiving head 440 is prevented from sliding off of the inner arm435.

The length adjusting member 437 may be a bolt or other similar devicethat acts to clamp the sliding inner arm 435 in place within the housingmember 341 of the telescoping arm assembly 430. The illustrated lengthadjusting member 437 is a threaded bolt that advances through a threadedopening 432 in the housing 431 upon rotation. A plunger 438 and spring439 are provided for insertion into the bolt 427, and exert a moderateamount of pressure against the inner arm 435 even when the bolt 427 isnot tightly clamped. The plunger thereby biases the inner arm 435 fromfreely sliding through the housing 431. In addition to telescopicsliding, the inner arm 435 may be rotated to adjust the position of therod receiving head 460, swinging the head forward and backward out ofthe plate of the plate member 410.

The telescoping arm assembly 430 may also be adjusted by pivoting thearm about a swivel connection 420 that couples the arm 430 to the platemember 410. The pivoting of the arm 430 shifts the rod receiving headlaterally outward or medially inward. The pivoting of the arm isprovided by a bolt 425 or other member that passes through an opening421 in the plate member 410 and is coupled to the telescoping arm. Inthe illustrated embodiment, the bolt 425 may be threadably coupled viaits threaded shank 426 to a threaded aperture 424 attached to thetelescoping arm assembly 430. Tightening of the bolt 425 clamps aportion of the plate member 410 between the telescoping arm 430 and thehead of the bolt 425, inhibiting movement therebetween. A circular arrayof teeth 423 may be provided around the threaded opening 424 in order toassist in preventing movement of the arm by meshing with complementaryteeth 427 surrounding the opening 421 on the back surface of the platemember 410. The meshing of the teeth when a clamping force is exerted bythe bolt 425 is much more effective for resisting pivotal movement ofthe arm 430 than reliance solely on friction between relatively flatsurfaces.

Another mechanism for adjusting the positioning of rod receiving devicesrelative to a plate member is shown in FIGS. 27 through 33. The platedevice 501 includes a pair of elongate guide tracks 515 in arm portions514 of the plate member 510. Sliding members 522 are disposed in theguide tracks, and are configured to slide therealong. A locking member520 inhibits movement of the sliding member 522 by clamping the slidingmember against the perimeter of the guide track 515 of the plate body510. A sliding washer member 521 assists in locking the sliding member522 in place.

Articulating arms 530 are coupled to the plate member 510 through thesliding members at ball and socket connections 523 and serve to positionrod receiving head members 560 configured to clamp to spinal rods orother elongate members. In the illustrated embodiment, the receivinghead members 560 include arcuate recesses 563 configured to cradlespinal rods, and a set screw clamping member 561 disposed in the headmember 560 and positioned to clamp the spinal rod against the arcuaterecess 563 when rotationally advanced.

The articulating arms 530 of the device 501 are provided with aplurality of articulating ball and socket connections for each armbecause they are joined to both the plate member 510 and the rodreceiving heads 560 by ball and socket connections. A single actuator535 simultaneously locks both ball and socket connections 523 and 567against movement, as will be described below.

One of the articulating arms 530 is shown in an exploded view in FIGS.29, 30, and 31 in order to demonstrate locking of the arm. The armportion 530 is a hollow sleeve-like member with narrowed collar portionsat each end that provide openings with a diameter less than the diameterof the internal bore of the arm portion. A sliding member 522 that isslidably disposed in the guide track 515 of the plate member is coupledto the articulating arm 530 by a ball and socket connection 523 formedby a spherical head 524 of the sliding member 522 and a spherical cavity528 of the arm portion 530. A side opening in the arm portion 530 allowsthe spherical portion 524 to be loaded into the cavity 528 of the arm530. Similarly, the rod receiving head 560 has a spherical portion 568that is received in a second spherical cavity 569 of the arm portion 530to form a second ball and socket connection 567.

A locking device including a threaded locking bolt 535, frictionelements 540 and 541, and a plate 536 is provided. Friction elements 540and 541 are disposed within a bore 531 of the arm portion 530, and havetapered ends 545 and 546 that are directed toward the center of the arm.The locking bolt 535 is threaded through the plate 536 so that turningof the bolt 535 advances the bolt downward through the arm 530. Taperedabutment surfaces 537 are provided along the exterior of the bolt, andadvancing the bolt 535 downward by a predetermined amount causes theabutment surfaces 537 to engage the tapered ends 545, 546 of thefriction elements, forcing the friction elements 540, 541 to slideoutward away from the bolt 535. The friction elements are thereby forcedinto contact with the spherical portion 524 of the sliding element andthe spherical portion 568 of the rod receiving head 560, clamping themagainst their respective cavities in the arm portion 530. Thus, themovement of the locking bolt 535 transverse to the arm portion 530 istranslated into axial locking forces along the axis of the arm 530 thatsimultaneously lock the two spherical portions 524 and 568 in place atopposite ends of the arm portion 530.

The relationship between the sliding element 522 and the guide track 515is more clearly shown in FIGS. 32 and 33, with the articulating armremoved for an unobstructed view of the plate member 510.

FIGS. 34-36 illustrate another occipital plate design with a pluralityof apertures 612 for anchor devices and an easy locking feature. Theplate 601 includes a pair of sliding members 623 partially disposed inguide tracks 610 for shifting laterally and medially. A single actuator630 for each sliding member 620 locks the position of the sliding memberwith respect to the plate and locks the position of a spinal rod withrespect to the sliding member. Each sliding member 620 includes anarcuate recess 623 for receiving a spinal rod. Adjacent the arcuaterecess is a flexible portion 625 of the sliding member. Tightening ofthe actuator 630 shifts the flexible portion 625 away from the actuator630, compressing the flexible portion 625 against a spinal rodpositioned in the neighboring arcuate recess 623.

Simultaneously with locking the rod, the actuator 630 secures thesliding member 620 with respect to the plate member 605. As best seen inthe partially exploded view of FIG. 35, the sliding member includes aclip 627 that holds the sliding member 620 along a guide track 610 inthe plate. The guide track 610 includes a wider inner space 615 and anarrower window 617 that is formed by partial enclosure of the innerspace 615 by a flange 613. The clip 627 of the sliding member isdisposed in the wider inner space 610 of the track, and connects to therest of the sliding member 620 through the narrow window 617. Thesliding member 620 may be connected to a pin 640 or another structurethat rides in a guide slot 645 to limit movement of the sliding member,preventing it from sliding out of the end of the guide track 610.

When the threaded portion 637 of the actuator 630 is advanced into athreaded throughbore 629 of the sliding member 620, the actuator abutsthe plate 605, pulling the sliding portion forward so that the clip 627abuts the flange 613 of the guide track. Friction between the clip 627and the flange 613 inhibits sliding of the sliding member 620. As can beseen from the view in FIGS. 35 and 36, the actuator 630 is also providedwith a tapered head 635 so that advancement of the actuator 630 causescamming of the tapered head 635 against the adjacent flexible portion625 of the sliding member. The resulting shifting of the flexibleportion 625 reduces the size of the arcuate recess 623, allowing thedevice to clamp an appropriately sized spinal rod positioned in thearcuate recess 623.

FIGS. 37-39 illustrate yet another plate device with articulatingmembers for positioning and securing a pair of spinal rods. The deviceincludes a plate member 705 having a plurality of openings 712 foranchor members and a pair of elongate clamp arms 710, each having aclamp jaw 715 moveably coupled to the arm. The arm further includes arod receiving recess 720 that can be seated on a spinal rod. An actuator730 associated with each arm draws the clamping jaw 715 upward, clampinga spinal rod between the arcuate surface 720 and the moveable jaw 715.

The arms 710 are able to pivot around a central bolt 750 that passesthrough both arms. Both arms are simultaneously secured against pivotingby tightening of the central bolt 750. As shown in FIGS. 38 and 39, thearms and plate are provided with arrays of teeth 755 and 757 on thefront and rear sides that mesh together when the bolt 750 clamps thearms 710 against the plate member 705. The plate member also includes acircular array of teeth 756 that meshes with corresponding teeth 757 ofthe arms 710. In order to pivot the arms 710, the teeth 755 must beallowed to slide past one another, pushing the arms away from oneanother and away from the plate. This, of course, is extremely difficultwhen the central bolt 750 clamps the arms 710 against the plate 705. Theteeth thus provide an effective inhibitor of relative motion between thearms 71 and the plate 705. if desired, washers with corresponding teethcan be positioned between the two arms and/or between the arms and theplate to adjust the distances therebetween.

A further occipital plate design with an easy locking feature is shownin FIGS. 40-43. The device 801 includes a plate body 810 including aplurality of openings for receiving anchor members. The plate bodyfurther includes a pair of recesses or grooves 815 for receiving aspinal rods. A pair of slidable locking elements 820 are provided thatmay slide to partially cover the recesses 815, blocking the exit of anappropriately-sized spinal rod positioned therein. The sliding members820 are both shifted by a central asymmetrical actuator 850. Due to theasymmetrical shape of the actuator 850, rotation of the actuator forcesthe sliding members simultaneously outward to cover the rod recesses 815and clamp spinal rods therein.

For instance, in the illustrated embodiment, a generally oblongrotatable actuator 850 is positioned between the two sliding members.When the longer dimension of the actuator 850 is oriented vertically,the sliding members may be positioned toward the center of the plate.However, rotating the actuator by 90 degrees to the locked positionshown in FIG. 40 causes camming of the wide portions of the actuatoragainst the sliding members 820, forcing the sliding members outward,simultaneously locking both rod recesses 815. Springs may be provided sothat the sliding members 820 return to their original positions when theactuator 850 is rotated back to the unlocked position.

FIGS. 44 and 45 illustrate an expansion screw that may be used to mountthe above-described occipital plates to the skull. The screw 900includes a threaded body 902 and a head portion 901. The body includesone or more slits 905 to divide the body into a plurality of expandablefingers that are capable of deflecting slightly outward. The screw alsoincludes an axial bore 903 through most of the body of the screw. Afterthe screw is threaded into a body surface, an insertable camming element920 may be linearly inserted through the bore 903, forcing theexpandable fingers 906 of the screw body slightly outward. Thisexpandable screw has greater holding power than traditional screws dueto the increased transverse force exerted by the camming insert and theoutwardly expandable finger portions. Thus, a shorter screw may be usedto mount the occipital plate, requiring less penetration into the boneof the skull.

In another aspect of the invention, a plate device as shown in FIGS.46-49 is provided in order to stabilize spinal rods. Similarly to thedevice shown in FIG. 14, the device 1010 shown in FIGS. 46-49 includes atrack member 1050 to which a pair of rod receiving or clamp members 1070are slidably connected, as shown in FIGS. 14-19. In the illustrateddevice, a locking actuator 1080 couples each clamp member 1070 to thetrack member 1050, and allows relative rotation between the clampmembers and the track member. The locking actuators 1080 are alsodisposed in guide slots 1052 formed in the track member 1050, as shownin FIG. 47, to allow sliding movement of the clamp members 1070 along alength of the track member 1050. The sliding and rotation of the clampmembers 1070 along the track member 1050 allows the distance between theclamp members to be adjusted so that the clamp members 1070 may capturespinal rods having various orientations and distances from one another.

Alternatively, the clamp members may be coupled to arm portions or otherportions of the plate device without requiring the device to include atrack member.

As with previous devices described in this application, the illustratedplate device 1010 of FIG. 46 has a plate body 1011 that includes anumber of throughholes 1012 for receiving screws or other devices formounting the plate device to the skull of a patient. Cuts or grooves1018 and 1019 in the plate body 1011 allows for bending of the plate tobetter accommodate the contours of the skull. Arms 1014 may beconfigured to hold the track member 1050 in a desired relationship withthe plate body 1011. If desired, the arms 1014 may be hinged orarticulated in order to allow the spatial relationship of the plate body1011 and track member 1050 to be varied, and locking members may beprovided to selectively prevent movement of the arms 1014 when the trackmember 1050 is positioned as desired.

The illustrated clamp members 1070 each include a body portion 1071 anda clamping jaw 1072 forming an arcuate recess 1073 for receiving andholding in place a spinal rod. As illustrated, the clamping jaw 1072 isa flexible portion of the clamp body that is secured against the spinalrod by the locking actuator 1080. Alternatively, the jaw portion 1072may be a separate portion that is pivotable with respect to the clampbody 1071. The design of the illustrated clamp member 1070 and lockingactuator are such that a single actuator 1080 causes each clampingmember 1070 to clamp a spinal rod in place and simultaneously locks theposition of that clamping member with respect to the track member 1050.

As best shown in the exploded view of FIG. 49, each clamping member 1070includes an arcuate recess 1073 for receiving a spinal rod. Adjacent thearcuate recess is a flexible portion 1072 of the clamping member. Thelocking actuator 1080 passes through a guide track opening 1052 of thetrack member 1050 to engage the clamp member 1070. A head portion 1082of each locking actuator 1080 is sized and configured so that it cannotpass through the guide track openings 1052 of the track member 1050,while the shank portion 1083 of the locking actuator 1080 is configuredso that it may be slidably disposed within a guide track opening 1052.

Rotation of the actuator 1080 engages threading 1081 of the actuatorwith a corresponding threaded bore 1078 of the clamp member 1070,coupling the clamp member 1070 to the track member 1050 and eventuallyclamping the track member 1050 between the head 1082 of the lockingactuator 1080 and the clamp body 1071 to fix the clamp 1070 againstsliding and rotation. Simultaneously, tightening of the locking actuator1080 shifts the actuator relative to the clamp member 1070 and engages acam surface 1085 of the actuator with the flexible clamping jaw 1072,shifting the flexible jaw portion 1072 away from the actuator 1080 andcompressing the flexible portion 1072 against a spinal rod positioned inthe arcuate recess 1073. In other words, rotation of the actuator 1080,for instance utilizing tool interface 1089, advances the lockingactuator 1080 to simultaneously clamp the clamp body 1070 against thetrack member 1050 and deflect resilient jaw portion 1072 of the clampingmember inward to lock a spinal rod in place.

It has been found that the unitary clamping device 1070 of FIGS. 46-49having a clamping body and deflectable jaw portion 1072 has exceptionalholding force when clamped into place with a rotatable screw-likeactuator 1080 as illustrated. The locking actuator, of course, may varyfrom the illustrated form, and can include, for instance, non-threadedengagement features such as discontinuous flanges configured to advancethe locking actuator 1080 upon rotation relative to the clamping member1070. The clamping member may be made of various materials, but ispreferably made from a flexibly resilient material such as Nitinol inorder to allow for locking and unlocking of the spinal rod.

It is intended for the following claims to cover these and any otherdepartures from the disclosed embodiment which fall within the truespirit of the invention.

What is claimed is:
 1. A posterior spinal stabilization systemcomprising: a plate body including a plurality of apertures forreceiving anchor members; a track member of the plate body including anelongate guide slot; at least one rod receiving member for receiving aspinal rod; a swivel base slideably disposed in the track member guideslot and having an arcuate head portion pivotally connected to the rodreceiving member so that the rod receiving member is operable to slidealong the guide slot with the arcuate head portion being spaced from thetrack member to allow pivoting of the rod receiving member about aplurality of different axes extending through the head portion; and aclamping member operable to fix the swivel base against sliding in theguide slot; wherein the clamping member is coupled to the track memberby a locking actuator operable to shift the clamping member between anunlocked configuration, wherein the swivel base is slideable along theguide slot, and a locked configuration, wherein the swivel base is fixedagainst sliding in the guide slot.
 2. The posterior spinal stabilizationsystem of claim 1, wherein the plate body includes a bone engagingportion having the plurality of apertures and the guide slot is orientedin a plane transverse to the bone engaging portion of the plate body. 3.The posterior spinal stabilization system of claim 1, wherein thearcuate head portion of the swivel base has a spherical configuration.4. The posterior spinal stabilization system of claim 1, wherein thearcuate head portion includes a compression gap for providing asnap-lock connection between the head portion and the rod receivingmember.
 5. The posterior spinal stabilization system of claim 1, whereinthe guide slot includes an access end opening to allow the swivel baseto be slid into the guide slot; and a shiftable stop member associatedwith the track member operable to block the end opening of the guideslot to keep the swivel base from exiting the guide slot.
 6. Theposterior spinal stabilization system of claim 1, further comprising alocking member operable to simultaneously fix the spinal rod to the rodreceiving member and fix the rod receiving member relative to thearcuate head portion of the swivel base.
 7. The posterior spinalstabilization system of claim 1, wherein the track member includes anupper side and a lower side, and the arcuate head portion of the swivelbase is spaced from the upper side of the track member.
 8. The posteriorspinal stabilization system of claim 1, wherein the track membercomprises a second elongate guide slot; and a second rod receivingmember for receiving an additional spinal rod; a second swivel baseslideably disposed in the second track member guide slot and having anarcuate head portion pivotally connected to the second rod receivingmember so that the second rod receiving member is operable to slidealong the second guide slot with the arcuate head portion being spacedfrom the track member to allow pivoting of the second rod receivingmember about a plurality of different axes; wherein the clamping memberis operable to fix each swivel base against sliding in the respectiveguide slots.
 9. A posterior spinal stabilization system comprising: aplate body including a plurality of apertures for receiving anchormembers; a track member of the plate body including an elongate guideslot; at least one rod receiving member for receiving a spinal rod; anda swivel base slideably disposed in the track member guide slot andhaving an arcuate head portion pivotally connected to the rod receivingmember so that the rod receiving member is operable to slide along theguide slot with the arcuate head portion being spaced from the trackmember to allow pivoting of the rod receiving member about a pluralityof different axes extending through the head portion; wherein the trackmember is connected to the plate body by an arm member configured tospace the track member from a patient's skull and toward the patient'sspine when the plate body is mounted to an occipital region of theskull.
 10. The posterior spinal stabilization system of claim 9, whereinthe arm member has a curved configuration to space the track member fromthe patient's skull and toward the patient's spine when the plate bodyis mounted to an occipital region of the skull.
 11. A posterior spinalstabilization system, comprising: a plate body including a plurality ofapertures for receiving anchor members; a track member of the plate bodyincluding an elongate guide slot; a yoke member for receiving a spinalrod; and a slideable connection between the yoke member and the trackmember configured to allow the yoke member to slide in the guide slotand to shift polyaxially with respect to the track member for receivingthe spinal rod in the yoke member in a selected one of a plurality ofdifferent orientations with respect to the track member; wherein thetrack member is connected to the plate body by an arm member that isconfigured to position the track member spaced from a patient's skulland toward the patient's spine when the plate body is mounted to anoccipital region of the skull.
 12. The posterior spinal stabilizationsystem of claim 11, further comprising a clamping member operable to fixthe yoke member relative to the guide slot, wherein the yoke member isoperable to shift polyaxially with respect to the track member when theyoke member is fixed with respect to the guide slot by the clampingmember.
 13. The posterior spinal stabilization system of claim 11,wherein the arm member has a curved configuration to space the trackmember from the patient's skull and toward the patient's spine when theplate member is mounted to an occipital region of the skull.
 14. Theposterior spinal stabilization system of claim 11, wherein the slideableconnection includes a swivel base slideably disposed in the guide slotand connected to the yoke member to allow the yoke member to shift alongthe guide slot, the swivel base including a spherical head portionconfigured to matingly engage with the yoke member to allow the yokemember to pivot polyaxially with respect to the spherical head portion.15. The posterior spinal stabilization system of claim 14, furthercomprising a locking member operable to simultaneously fix the spinalrod to the yoke member and fix the yoke member relative to the swivelbase.
 16. The posterior spinal stabilization system of claim 11, whereinthe guide slot includes an access end opening to allow the yoke memberto be slideably connected to the guide slot; and a shiftable stop memberassociated with the track member operable to block the end opening ofthe guide slot to keep the yoke member from exiting the guide slot. 17.A posterior spinal stabilization system, comprising: a plate bodyincluding a plurality of apertures for receiving anchor members; a trackmember of the plate body including an elongate guide slot; a yoke memberfor receiving a spinal rod; a slideable connection between the yokemember and the track member configured to allow the yoke member to slidein the guide slot and to shift polyaxially with respect to the trackmember for receiving the spinal rod in the yoke member in a selected oneof a plurality of different orientations with respect to the trackmember; a clamping member operable to fix the yoke member relative tothe guide slot, wherein the yoke member is operable to shift polyaxiallywith respect to the track member when the yoke member is fixed withrespect to the guide slot by the clamping member; and a locking actuatoroperable to shift the clamping member between an unlocked configuration,wherein the yoke member is shiftable along the guide slot, and a lockedconfiguration, wherein the yoke member is fixed with respect to theguide slot.
 18. A posterior spinal stabilization system, comprising: aplate body including a plurality of apertures for receiving anchormembers; a track member of the plate body including an elongate guideslot; a yoke member for receiving a spinal rod; a slideable connectionbetween the yoke member and the track member configured to allow theyoke member to slide in the guide slot and to shift polyaxially withrespect to the track member for receiving the spinal rod in the yokemember in a selected one of a plurality of different orientations withrespect to the track member; wherein the slideable connection includes aswivel base slideably disposed in the guide slot and connected to theyoke member to allow the yoke member to shift along the guide slot, theswivel base including a spherical head portion configured to matinglyengage with the yoke member to allow the yoke member to pivotpolyaxially with respect to the spherical head portion; and an insertmember engaged with the spherical head portion within the yoke memberfor forming a ball and socket connection with the spherical headportion, the insert member being configured to engage the spinal rod.